I quite agree with this view point. If startup is your goal, (good) incubators will better serve towards that objective. So if your logic is: do an MBA, learn biz skills, then do a startup, I would really question that logic. Startups work differently and that's why getting into the market directly helps a lot more. The skills learned in a (good) MBA program are still required in a startup world (soft skills, communication skills, business acumen etc.), but you can find other ways to make up for them.
Also, I can confidently recommend starting up as early as possible, preferably in your early to mid 20s.